1. Field of the Invention
The present invention relates to a circular polarization microstrip line antenna, a power supply and a receiver loading the microstrip line antenna and, particularly, to a circular polarization microstrip line antenna used to transmit and receive in a satellite broadcasting or a satellite communication, a power supply and a receiver loading the microstrip line antenna.
2. Description of the Prior Art
A microstrip line is patterned on the surface of a board in a microstrip line antenna, and an overall ground plane is formed on the rear surface of the board. The individual microstrip lines are bent in a predetermined periodic wave shape such as a square wave, and a plurality of the microstrip lines are aligned at a suitable interval to constitute an antenna array. A power supply is provided at one end of the microstrip line, and a matching load is provided at the other.
A coaxial cable is normally used at the power supply. A central conductor of the coaxial cable is inserted from below into a hole perforated along the edge of the board, and the end is soldered to one end of the microstrip line. This soldering is extremely complicated. As the number of the microstrip lines of the antenna array is increased, the soldered parts are increased to be inefficient. An insulating tube conductor of the coaxial cable is connected to the ground plane of the rear surface of the board.
When a transmission is executed by such a microstrip line antenna, a high-frequency current of a predetermined frequency band (e.g., 12 GHz) is supplied by the coaxial cable. The high-frequency current is periodically bent in its traveling direction by carrying along the microstrip line. A left-handed circularly polarized wave is radiated if the microstrip line is a left-handed circular polarization antenna or a right-handed circularly polarized wave is radiate if the microstrip line is a right-handed circular polarization antenna by the synergistic action of the time and spatial sine wave of the high-frequency current and the spatial shape of the microstrip line. If the microstrip line antenna is a vertical polarization antenna, a vertically polarized wave is radiated, or if the microstrip line antenna is a horizontal polarization antenna, a horizontally polarized wave is radiated.
Since the antenna can be used for both the transmission and the reception by the same configuration, the polarized wave having the same characteristics as the radiated polarized wave can be naturally received by the microstrip line antenna used for the transmission. That is, if the microstrip line antenna is a left-handed circular polarization antenna, a left-handed circularly polarized wave can be received, or if the microstrip line antenna is a right-handed circular polarization antenna, a right-handed circularly polarized wave can be received. If the microstrip line antenna is a vertical polarization antenna, a vertically polarized wave can be received, or if the microstrip line is a horizontal polarization antenna, a horizontally polarized wave can be received.
The received polarized wave having predetermined characteristics is input to a receiver via the coaxial cable. The receiver demodulates the input frequency energy via an amplifier, a filter and a mixer and outputs the demodulated wave.
In the circular polarization microstrip line antenna in which the periodic wave shape of the microstrip line antenna is a square wave shape, the lengths of the upper side, the lateral side and the bottom of the square wave shape have predetermined correlation with respect to the line wavelength g of a traveling wave propagated on the microstrip line. The "predetermined correlation" is not univocal for the line wavelength g, but various relational expressions have been heretofore proposed. The purpose of the proposal is to enhance the directivity of the circularly polarized wave, and to ultimately form a completely circularly polarized wave (a circularly polarized wave having 0 dB of the axial ratio of a long axis to a short axis), but it is not yet satisfied.
Since a conventional circular polarization microstrip line antenna has a configuration for transmitting and receiving only one of left-handed and right-handed circularly polarized waves, to receive and transmit both the left-handed and right-handed circularly polarized waves, it is necessary to prepare two of a microstrip line antenna for a left-handed circularly polarized wave and a microstrip line antenna for a right-handed circularly polarized wave and to connect them to a power supply, resulting in an increase in an entire size and complexity in an assembling and installing works.
It is convenient if both the left-handed and right-handed circularly polarized waves transmitted from one satellite can be received by one circular polarized microstrip line antenna. In this case, it is necessary to remarkably increase the directivity of the circular polarization microstrip line antenna. Accordingly, it is insufficient by a numeric value of the above-mentioned official gazette proposed at present.
Since the conventional receiver is constituted to process only a certain specific polarized wave, if the receiver receives a left-handed or right-handed polarized waves or a vertical or horizontal linearly polarized wave, it is necessary to install microstrip line antennas corresponding to the polarized waves and to prepare receives for the respective microstrip line antennas, and an overall increase in size cannot be avoided.
It therefore becomes necessary to solve the above-mentioned technical problem, so that the connecting configuration of the circular polarization microstrip line antenna to the power supply and the configuration of the power supply are simplified to enhance the efficiency of the assembling work, to simultaneously remarkably enhance the directivity, to transmit and receive both the left-handed and right-handed circularly polarized waves by one circular polarization microstrip line antenna while approaching the axial ratio to 0 dB and further to receive various polarized waves by one receiver, thereby improving the convenience of the antenna of this time, the power supply and the receiver. The object of the present invention therefore is to solve the above-mentioned technical problem.